This invention relates to magnetic tape cassettes, and more specifically to improvements in a magnetic tape cassettes comprising an intermediate frame and clear top and bottom plates.
The present applicant previously proposed a magnetic tape cassette having a case composed of a metallic intermediate frame and clear plastic plates fastened to the upper and under surfaces of the frame. (Japanese Utility Model Application No. 126245/1977) The intermediate frame of die-cast aluminum or the like keeps the clear top and bottom plates from being deformed thermally or otherwise, for example, with molding strains, ensuring very smooth winding and unwinding of the magnetic tape. It eliminates the usual causes for off-track recording or playback, irregular reeling of the tape, variations in the reproduction output, and other troubles. However, the metal working such as die casting of aluminum takes much time and labor and, moreover, calls for additional, complicate processes for surface finish, improved corrosion resistance, etc. On the other hand, the ordinary magnetic tape cassettes in wide use, which does not use the sandwich structure but a pair of plastic half cases fastened together, pose the problems of molding strains and thermal deformation. These and other shortcomings made the two-member cassettes unsuitable for applications where accuracy is the prime consideration. In other applications, also, there are additional difficulties.